Castellated nozzle and method of use thereof

ABSTRACT

A castellated nozzle for connecting a plurality of microelectronic leads to an associated plurality of contact pads and method of using the same. The castellated nozzle includes a body having a plurality of castellations protruding therefrom, with each of the castellations having a contact surface thereon. A channel is formed adjacent to at least one castellation of the plurality of castellations. An opening extends through the body for introducing a heated gas therein. The contact surfaces of the plurality of castellations are aligned to a respective plurality of leads. Typically, the castellated nozzle includes a first plurality of castellations forming a first row and a second plurality of castellations forming a second row.

This application is a division of application Ser. No. 08/388,327 filedFeb. 14, 1995 which application is now U.S. Pat. No. 5,593,083.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention generally relates to microelectronic packaging.More particularly, the present invention relates to tools employed tointerconnect semiconductor chip packaging structures to semiconductorpackaging substrates. Even more particularly, the present inventionrelates to apparatuses employed to solder bond a plurality ofmicroelectronic leads to their respective contact pads.

2. Background Information

As is well known, soldering represents a common technique employed innumerous joining applications in microelectronics. In accordance withthese well-known soldering techniques, flexible circuit carriers arewidely used in the design of microelectronic packages to connect variousmicroelectronic packages and devices to one another. For instance, aflexible circuit carrier may be used to interconnect a semiconductorchip packaging structure, such as a multi-chip module, and asemiconductor packaging substrate, such as a printed circuit board.

A problem associated with the design of microelectronic packages is therequirement of providing sound electrical connections between arelatively large number of extremely small conductive leads, i.e.,signal, ground, and power conductors, and their respective contactlocations. These contact locations, i.e., contact pads, may be appliedto a semiconductor chip or other circuit location in a wide variety ofconfigurations. In the microelectronics industry, the precise alignmentof a plurality of conductive leads on one semiconductor device to anassociated plurality of contact pads on another semiconductor devicepresents a significant problem. Often, in order to achieve the precisealignment required between the miniature conductive leads and theirrespective contact pads, sophisticated and expensive alignment systemsare necessary. Such systems typically are programmed to achieveextremely close alignment tolerances.

Furthermore, it is often necessary to force the leads, once properlyaligned, into contact with their respective contact locations. However,forcing a large plurality of microelectronic conductive leads intocontact with a like plurality of contact pads requires a tool which canbe precisely aligned so that the leads can be properly displaced to makecontact with their associated contact locations. Another device is alsoneeded to heat the contact pads to a temperature sufficient to melt thesolid solder thereon so that solder joints can be formed.

As will be disclosed herein, the present invention defines an apparatusand method of using a castellated nozzle for forming sound electricalconnections between a semiconductor chip packaging structure, such as amulti-chip module, and a packaging substrate, such as a printed circuitboard, without the need for a sophisticated alignment system. Thesesound electrical connections are achieved notwithstanding the need toforce a plurality of leads into contact with their respective contactlocations. As will be further defined, such connections can be achievedby soldering. Moreover, the apparatus and method as described hereinpermits the fluxless solder bonding of conductive leads to theirassociated contact pads.

The present invention provides a significant improvement over currentlyknown microelectronic soldering devices which effect electricalconnections in miniaturized electronic packages and is applicable totape automated bonding (TAB) technology. The apparatus as defined hereinassures Strong electrical connections between extremely smallmicroelectronic circuit elements. The apparatus is relatively simple touse, and can be adapted to mass production techniques, thus reducing theoverall cost of the final package structure.

Thus, a need exists for an apparatus which simplifies soldering andconnection of a plurality of miniaturized microelectronic elements. Thestructure and method of use of the present invention contains a solutionto the aforementioned problems. As defined below, the present inventionprovides a significant improvement over currently known solderingtechniques for performing electrical connections in miniaturizedelectronic packages.

SUMMARY OF THE INVENTION

Briefly, the present invention satisfies this need and overcomes theshortcomings of the prior art through the provision of a castellatednozzle for connecting a plurality of leads to a plurality of contactpads, which includes a body having a plurality of castellationsprotruding therefrom, with each of the castellations having a contactsurface thereon. A channel is formed adjacent to at least onecastellation of the plurality of castellations. An opening extendsthrough the body of the nozzle for providing a heated gas to theplurality of channels. A means for aligning the contact surfaces of theplurality of castellations to a respective plurality of leads is formedthrough the body of the castellated nozzle.

The castellations and channels may form a first row and a second rowthereof, with the opening separating the first row from the second row.The opening may define a first inner wall opposing a second inner wall.Both walls may be substantially parallel to one another. The first andsecond inner walls may form an inner edge of the castellations andchannels. The opening which extends through the body of the nozzle mayhave a bottom open end and a top open end.

The contact surface of each castellation may include an outer edge. Aplanar surface may extend from the outer edge of the contact surface toan outer wall of the castellated nozzle body. At the outer edge of eachcastellation, the contact surface may intersect the planar surface.Also, each of the channels may form a channel surface extending from itsinner edge to the outer wall of the castellated nozzle body.

Typically, the plurality of leads are located on a flexible circuitcarrier. A plurality of apertures are formed on the flexible circuitcarrier in the same configuration as the plurality of castellations.Each one of the plurality of conductive leads has a portion whichbridges a respective aperture of the plurality of apertures.

The present invention will typically include a substrate having aplurality of contact pads deposited thereon in the same configuration asthe plurality of apertures. Both the flexible circuit carrier and thesubstrate preferably have a means for alignment with one another and tothe castellated nozzle.

In order to effect operation of the castellated nozzle of the presentinvention, the flexible circuit carrier is aligned and mated with thesubstrate so that each of the plurality of contact pads is positionedproximate to a respective aperture of the plurality of apertures.Because of the thickness of the layers of the semiconductor devices, agap may separate each of the plurality of contact pads from each portionof the plurality of leads which bridge the plurality of apertures.

In order to facilitate contact of the leads to their respective contactpads, the castellated nozzle is aligned and mated with the flexiblecircuit carrier so that each of the contact surfaces of thecastellations contacts a respective portion of each of the plurality ofleads which bridge the plurality of apertures. Once proper alignment isachieved, the castellated nozzle may be forced in a direction so as todisplace the leads so that they contact their respective contact pads.

The castellated nozzle may include a hole to facilitate alignment andmating of the castellated nozzle to the flexible film carrier.Typically, the hole has a longitudinal axis that passes through thecastellated nozzle body in a direction parallel to the inner walls ofthe opening. The flexible circuit carrier and substrate may have similarholes formed therethrough. A pin may then be inserted through theseholes for alignment and mating.

Typically, a hot air thermode (HAT) tool will be placed in closeproximity to the bottom of the castellated nozzle so that a hot gas canbe introduced into the opening extending through the body of thecastellated nozzle for melting the solid solder on the contact pads.Preferably, the gas comprises nitrogen. As the gas travels through theopening it will flow into the channels of the nozzle, thereby creatingeddies in the contact pads and exposing fresh solder for forming solderjoints.

Preferably, the flexible circuit carrier is comprised of polyimide. Thesubstrate may be a printed circuit board.

In one embodiment of the present invention, the castellated nozzleincludes a first plurality of castellations forming a first row thereof,each of the first plurality of castellations having a contact surfacethereon, a first plurality of channels formed adjacent to at least onecastellation of the first row, a second plurality of castellationsforming a second row thereof, each of the second plurality ofcastellations having a contact surface thereon, and a second pluralityof channels each of which is formed adjacent to at least onecastellation of the second row. An opening is formed between the firstrow and the second row. Preferably, the first and second plurality ofcastellations are arranged in a staggered format, wherein at a firstpoint along the length of the opening, one of the castellations in thefirst row is located opposite to one of the channels in the second row.In addition, at a second point along the length of the opening, one ofthe channels in the first row is located opposite to one of thecastellations in the second row. The castellated nozzle may also includea means for aligning the plurality castellations to a respectiveplurality of leads. The means for aligning the castellated nozzlepreferably comprises one or more holes positioned between the first andsecond rows for receiving a pin to secure and align the flexible circuitcarrier to the castellated nozzle.

It is therefore a primary object of the present invention to enhance theart of electronic packaging.

It is another object of the present invention to reduce costs associatedwith connecting a large plurality of conductive leads to a likeplurality of contact pads.

It is yet another object of the present invention to provide anapparatus for connecting a large plurality of microelectronic conductiveleads to an equal number of contact pads, without the need for asophisticated alignment system.

It is still another object of the present invention to provide acastellated nozzle for connecting a plurality of microelectronic leadsto a plurality of contact pads which provides better electricalconnections by less costly assembly methods.

It is another object of the present invention to provide an apparatusfor connecting a plurality of conductive leads to a like plurality ofcontact pads by fluxless solder bonding.

It is a further object of the present invention to provide an apparatuswhich can displace a plurality of microelectronic conductive leads intocontact with a respective number of contact locations so that the leadscan be solder bonded to their respective contact pads.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter which is regarded as the present invention isparticularly pointed out and distinctly claimed in the concludingportion of the specification. The invention, however, both as toorganization and method of practice, together with the further objectsand advantages thereof, may be best understood by reference to thefollowing detailed description taken in conjunction with theaccompanying drawings in which:

FIG. 1 is a isometric view of a castellated nozzle in accordance withthe principles of the present invention.

FIG. 2 is a top view of the castellated nozzle of FIG. 1.

FIG. 3 is a front elevational view of the castellated nozzle of FIGS.1-2.

FIG. 4 is a side elevational view of the castellated nozzle of FIGS. 1-3having an alignment pin of the present invention positioned above thecastellated nozzle.

FIG. 5 is a partially cut-away and blown-up top view of a flexiblecircuit carrier of the present invention, having conductive leadsbridging apertures formed on the flexible circuit carrier.

FIG. 6 is a partially cut-away and blown-up top view of the flexiblecircuit carrier of FIG. 5 overlying a semiconductor substrate having aplurality of contact pads formed thereon, wherein the contact pads arealigned underneath respective apertures of the flexible circuit carrier.

FIG. 7 is a partially cut-away and blown-up sectional isometric view ofthe flexible circuit carrier of FIG. 6, showing the conductive leadsformed over the apertures of the flexible circuit carrier and contactpads formed on top of a semiconductor substrate.

FIG. 8 is a isometric view of a hot air thermode (HAT) tool employed inaccordance with the principles of the present invention for soldering aplurality of conductive leads to their respective contact pads.

FIG. 9 is a partially cut-away and blown-up view of the resultantconnection of the flexible circuit carrier and the substrate of FIGS.6-7 made in accordance with the principles of the present invention.

FIG. 10 is a top view of a multi-chip module attached to a printedcircuit board through the provision of four flexible circuit carriers inaccordance with the principles of the present invention.

FIG. 11 is a side elevational view of a flexible circuit carrierinterconnecting a printed circuit board and multi-chip module.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

It will be readily apparent that the components of the presentinvention, as generally described and illustrated in the figures, couldbe arranged and designed in a wide variety of different configurations.Thus, the following detailed description of the presently preferredembodiments of the castellated nozzle of the present invention, asrepresented in FIGS. 1-11, is not intended to limit the scope of theinvention, as claimed, but is merely representative of the presentlypreferred embodiments of the invention. The presently preferredembodiments of the invention will be best understood by reference to thedrawings, where like parts are designated with like numerals.

In reference to the drawings, and more particularly to FIG. 1, there isshown in accordance with the present invention, a castellated nozzle 10.Castellated nozzle 10 may have a body 11, which includes a first row 14and a second row 16 of castellations 12. Castellations 12 adjacent toone another may each have a channel 18 formed therebetween so as tocreate a first row 14 and a second row 16 of channels 18. An elongateopening 20 may extend through body 11 of castellated nozzle 10,separating first row 14 from second row 16. Castellated nozzle 10 mayinclude a means 22 for aligning castellated nozzle 10 to amicroelectronic packaging structure or substrate, the details of whichwill be described more thoroughly hereinafter.

As can be seen in FIG. 1, the body 11 of castellated nozzle 10preferably resembles the shape of a house. First row 14 and second row16 of castellations 12 and channels 18, for instance, take on an angledor sloped configuration like the roof of a house. Therefore, eachcastellation 12 may extend downward in a sloped configuration from acontact surface 19 to an outer wall 28. Each channel 18 may also takethe same sloped configuration. While the length of each castellation infirst row 14 is less than the length of each castellation in second row16, it should be understood that the respective lengths of rows 14 and16 is not intended to be in any way limiting.

As shown best in FIG. 1, each castellation 12 can have a contact surface19 at the uppermost surface of castellated nozzle 10. Each castellation12 may represent an elevated section on the body of the castellatednozzle 10. Preferably, contact surface 19 is flat and substantiallysquare or rectangular in shape. Contact surface 19 may include an outeredge formed thereon. As shown in FIG. 2, each of the plurality ofcastellations may form a planar surface 90 extending from the outer edgeof contact surface 19 to outer wall 28 of the castellated nozzle body.The contact surface 90 may intersect the planar surface 90 at the outeredge of each of the plurality of castellations. Contact surface 19 canlie in a plane perpendicular to an inner wall 26 of opening 20.Typically, each contact surface 19 may have the dimensions 0.010 by0.010 inches. Each contact surface 19 may be employed to make contactwith a conductive lead of an electronic device, the details of whichwill be described more fully hereinafter.

The first row 14 and second row 16 of castellations 12 are preferablyarranged in a staggered format so that at a point along the length ofelongate opening 20 a castellation 12 from first row 14 is located onone side of opening 20 and at the same point along the length of opening20 a respective channel 18 from second row 16 is located on the oppositeside of opening 20. Thus, each castellation 12 in first row 14 isaligned directly across from a respective channel 18 in second row 16 onthe opposite side of elongate opening 20, and vice versa. As such, eachcastellation 12 of first row 14 may be diagonal to at least one channel18 of second row 16.

While a definite number of castellations 12 is depicted in theaccompanying drawings, it should be understood that the number depictedis not limiting. Therefore, it is intended that the number ofcastellations 12 selected for castellated nozzle 10 be dependent uponthe number of solder joints to be effected in a microelectronic package,i.e., the number of solder joints between conductive leads andassociated contact pads between two semiconductor devices.

Preferably, opening 20 of castellated nozzle 10 extends substantiallylengthwise through body 11 of nozzle 10. The interior of castellatednozzle 10 therefore resembles a void. Inner walls 26 structurally defineelongate opening 20. As shown in FIG. 1, inner walls 26 may be parallelto one another and perpendicular to contact surfaces 19. Inner walls 26may form an inner edge for the castellations and channels. Each channel18 may have a channel surface 92 (FIG. 3) extending from its inner edgeof inner walls 26 to outer wall 28 of the castellated nozzle body. Eachchannel surface 92 may be in a plane parallel to the planar surfaces 90of each castellation 12 in the respective row. Each channel surface 92may be formed perpendicular to the walls of adjacent castellations 12.Opening 20 opens at the bottom of castellated nozzle 10 and provides athoroughfare for a gas to enter. Therefore, opening 20 may pass throughthe body of castellated nozzle 10, forming a bottom open end and a topopen end. The top open end can be proximate to the contact surfaces 19of the plurality of castellations 12. Operationally, after gas entersfrom the bottom open end of castellated nozzle 10, it may travel throughopening 20 and be dispersed into the plurality of channels 18 whichseparate adjacent castellations 12. A hot air thermode (HAT) tool may beemployed to introduce the gas to castellated nozzle 10 (FIG. 8).

FIG. 2 depicts castellated nozzle 10 from the top view. As can be seenfrom FIG. 2, each castellation 12 of first row 14 can extend a lengthless than each castellation 12 of second row 16. A support plate 21 maybe anchored in opening 20 so as to improve the structural integrity ofcastellated nozzle 10. Means 22 for aligning the castellated nozzle 10to a semiconductor packaging structure or other semiconductor substratemay comprise a hole 22 formed through body 11 of castellated nozzle 10.Hole 22 may be employed to accommodate an alignment pin 23 for aligningcastellated nozzle 10 to a semiconductor surface or substrate (FIG. 4).

Castellated nozzle 10 may include a bore 30 which passes through body 11of castellated nozzle 10. Preferably, there are two bores 30 extendingthrough the second row 16 of castellations 12 and channels 18. Bores 30may pass through the channel surface of channels 18 and the planarsurface of castellations 12. As can be seen in FIG. 2, bores 30 mayextend in a direction orthogonal to contact surface 19 and parallel toinner walls 26. Bores 30 may be threaded to accommodate a threaded bolt32. A spring 34 may be mechanically secured to bolt 32. As shown inFIGS. 3-4, bolt 32 and spring 34 both may protrude out of body 11 ofcastellated nozzle 10. Spring 34 may be employed to facilitate thebalancing of the castellated nozzle 10 on top of another semiconductordevice, the details of which will be disclosed more fully hereinafter.

FIG. 2 depicts the staggered relationship of the castellations 12 infirst row 14 to the castellations 12 in second row 16. For purposes ofillustration, a line 15 has been drawn in FIG. 2 to show therelationship between a castellation 12 of second row 16 to a channel 18of first row 14. As can be seen with line 15, each castellation 12 insecond row 16 may be aligned directly across elongate opening 20, from arespective channel 18 of first row 14, and vice versa.

While castellated nozzle 10 may be fabricated from any suitablematerial, it is preferred that castellated nozzle 10 be made of a hardmetal, such as 304 Stainless Steel, Inconel, and titanium. Thecastellated structure of nozzle 10 is preferably fabricated by acomputer controlled metal fabrication process, such as a wireelectro-discharge machining (EDM) method of manufacture.

FIG. 5 is a partially blown-up view, as seen from the top, of aninterconnector, i.e., a flexible circuit carrier 40, made in accordancewith the principles of the present invention. Flexible circuit carrier40 is preferably fabricated of a flexible insulative layer 42, such aspolyimide. A suitable material for insulative layer 42 is known underthe tradename Kapton®. Typically, insulative layer 42 has a thickness of2/1000th of an inch. By utilizing flexible circuit carrier 40 as themeans for interconnecting a semiconductor chip packaging structure to apackaging substrate, better electrical connections may be achievedbetween two semiconductor devices. While polyimide or Kapton® is thepreferred material for insulative layer 42 of flexible circuit carrier40, other suitable insulator materials may be selected therefor, such aspolyester.

A plurality of apertures 44 may be formed in insulative layer 42. Asshown in FIG. 5, a first row 46 and second row 48 of apertures 44 may beformed in layer 42. First and second rows 46, 48 of apertures 44resemble a series of "windows" on flexible circuit carrier 40. Any knownsemiconductor processing technique may be utilized to form apertures 44in layer 42, such as a known chemical photoprocessing method.

First row 46 and second row 48 of apertures 44 preferably are in astaggered format in a like fashion to castellations 12 of castellatednozzle 10 so as to facilitate alignment of each castellation 12 to arespective aperture 44. Therefore, each aperture 44 in first row 46 ispreferably diagonal to at least one aperture in second row 48.Preferably, each aperture 44 is bridged by an associated conductive lead49. Each conductive lead 49 may therefore be suspended over anassociated aperture 44. Each conductive lead 49 may be copper plated oranother suitable conductive metal. The portion of each lead 49 whichbridges aperture 44 may be coated with a solder wettable material, suchas gold. While gold is preferred in forming a solder wettable surfacewithout using flux on the bridged portions of conductive leads 49, othersuitable materials may be chosen, for example, nickel and tin.Typically, each conductive lead 49 may be about 4/1000th of an inch wideand 1/1000th of an inch in depth.

Flexible circuit carrier 40 includes an alignment means 50 so as tofacilitate alignment and proper mating of carrier 40 to a semiconductorsubstrate, such as a printed circuit board. Alignment means 50 may alsobe employed to align castellated nozzle 10 to the flexible circuitcarrier 40. Alignment means 50 may include a hole 50, which is formedduring fabrication of the plurality of apertures 44. By forming hole 50during fabrication of apertures 44, alignment means 50 can be formedprecisely in relation to apertures 44 and conductive leads 49.Therefore, sophisticated alignment systems, such as split optics, arenot necessary for aligning and properly mating flexible circuit carrier40 to a semiconductor packaging substrate and to castellated nozzle 10.

The present invention may be applied to tape automated bonding (TAB)technology. In TAB technology, a spaced plurality of leads, such asconductive leads 49, are fabricated on an elongated flexible carrierfilm, such as flexible circuit carrier 40, which can then be wound ontoand unwound from reels for automated fabrication of electroniccomponents. Each lead has an inner lead bond (ILB) end and an outer leadbond (OLB) end. Therefore, the conductive leads 49 formed on theflexible circuit carrier 44 may project inwardly where they extend overthe edge of the carrier film in a cantilevered fashion to form ILB ends.These inner conductive leads can thus be electrically connected tocontact pads on a semiconductor chip packaging structure, such as amulti-chip module (MCM) (FIG. 10). The outer conductive leads extendoutward over their respective apertures 44 in the carrier 40, therebyforming OLB ends. These outer conductive leads can thus be electricallyconnected to contact pads on a semiconductor packaging substrate, suchas a printed circuit board (FIG. 10). The flexible circuit carrier 44may be punched out by a die to take a specific configuration. Oneconfiguration for flexible circuit carrier 44 is a Z-shape, as shown inFIG. 11.

FIG. 6 depicts flexible circuit carrier 40 properly positioned atop asemiconductor packaging substrate 52, such as a printed circuit board.Substrate 52 includes a series of contact pads 54 deposited thereon.Contact pads 54 are deposited on substrate 52 in the same staggeredformat as apertures 44 of flexible circuit carrier 40 and castellations12 of castellated nozzle 10. Each contact pad 54 may comprise a copperland 56, topped by a solder coating 58 (FIG. 7). Each contact pad 54 isapplied to substrate 52 by using techniques well-known in the art. Eachcontact pad 54 preferably comprises the configuration as shown in FIG.7, having an oval shape and a dome-shaped upper portion. It should beunderstood however that the present invention is not limited to such aconfiguration, and numerous other configurations may be appropriate.

Semiconductor packaging substrate 52 preferably includes a hole 54,which can be aligned with hole 50 of flexible circuit carrier 42.Alignment pin 23 described above may be passed through holes 50 and 54so that flexible circuit carrier 40 and packaging substrate 52 may beproperly aligned to one another. Alignment of flexible circuit carrier40 to substrate 52 involves alignment of the two semiconductor devicesso that each contact pad 54 is properly situated under a respectiveaperture 44 or "window". Proper alignment of carrier 40 and substrate 52may be achieved when each aperture 44 of carrier 40 is positioned sothat a respective contact pad 54 is disposed underneath and proximate toaperture 44. Preferably, each aperture 44 should be superimposed overits respective contact pad 54. A fixture (not shown) may also bepositioned underneath substrate 52, which may also include a hole (notshown) for alignment pin 23 to pass through.

FIG. 7 is a sectional isometric view, taken along line A--A of FIG. 6,where conductive leads 49 can be seen cantilevered over respectiveapertures 44 of flexible circuit carrier 40. Underneath flexible circuitcarrier 40 is substrate 52 having a plurality of contact pads 54deposited thereon. Preferably, a solder dam, or a solder mask 60 isformed on substrate 52, and separates adjacent contact pads 54. Soldermask 60 may be applied to substrate 52 so as to prevent melted solderfrom running or migrating. In order to prevent melted solder frommigrating onto other leads on substrate 52, the thickness of solder mask60 is preferably greater than the thickness of contact pad 54, as can beseen in FIG. 7. Because the combined thickness of solder mask 60 andinsulative layer 42 is greater than the thickness of contact pad 54, agap 57 may separate each conductive lead 49 from its respective contactpad 54. Therefore, in order to make contact of each lead 49 to itsassociated contact pad 54 for forming a solder joint, displacement ofeach of lead 49 is necessary. At a minimum, each lead 49 must bedisplaced the distance represented by gap 57 so as to achieve thenecessary contact for forming the solder joints.

Once flexible circuit carrier 40 is properly aligned to substrate 52 sothat mounds 54 are situated under apertures 44, castellated nozzle 10may be employed to force each lead 49 to make contact with itsrespective contact pad 54. In order to properly align castellated nozzle10 to flexible circuit carrier 40, alignment pin 23 as described abovemay be employed. Springs 34, which protrude body 11 of castellatednozzle 10, provide a means for balancing nozzle 10 atop of flexiblecircuit carrier 40 so as to prevent castellated nozzle 10 from tippingover during operation.

While a staggered format is preferred for the castellations 12 andchannels 18 of castellated nozzle 10, it should be understood thatnumerous other configurations are acceptable, so long as theconfiguration chosen for castellated nozzle 10 is identical to theconfiguration chosen for the apertures of flexible circuit carrier 40and the contact pads 54 of substrate 52.

FIG. 8 depicts a hot air thermode (HAT) tool 70 for supplying asuperheated gas for solder bonding the leads to contact pads, asdescribed hereinabove. HAT tool 70 includes a body 72, a gas manifold74, one or more heating elements 76, and a nozzle head 78. The gasshould be sufficiently heated to melt the solid solder coating 58 andhave sufficient momentum to disperse the surface oxide formed on themolten solder. Gas manifold 74 can supply a steady flow of gas into thebody 72 of HAT tool 70. The gas is heated by raising the bodytemperature of body 72 by passing more current through heating elements76 and thereafter forcing the gas at a high velocity through nozzle head78. Preferably, nitrogen gas is selected to melt the solid solder.However, it is understood that numerous other gases may also besubstituted therefor. For example, compressed air may be employed.

As already described, HAT tool 70 may be employed to supply hot gas formelting solder coating 58 so that each lead 49 may be soldered to itsrespective contact pad 54. Further detail concerning the melting ofsolder coating 58 through the provision of the HAT tool used inaccordance with the principles of the present invention, and, asdescribed herein, may be found in U.S. Pat. No. 4,937,006, entitled"Method and Apparatus for Fluxless Solder Bonding", which is herebyincorporated by reference in its entirety.

The apparatus and method as described herein permits the fluxless solderbonding of conductive leads to associated contact pads. Instead ofutilizing flux to break up the oxide film formed on the solder coatings54, the oxide film may be broken as eddies are created as a result ofthe high momentum of the gas passing over the solder coatings 54. Oncefresh solder is available to gold plated copper leads 49, metallurgicalcontact may be instantly made.

Operationally, flexible circuit carrier 40 of the present invention canbe simply aligned to semiconductor packaging substrate 52 without theneed for a sophisticated vision system. Mechanical alignment andattachment may be secured through interference fits and slip fitsbetween pin 23 and alignment holes 50 and 54 of flexible circuit carrier42 and substrate 52, respectively. The same interference and slip fitsare used to align castellated nozzle 10 to the two semiconductorsurfaces. Alignment of the two semiconductor devices may be achieved byinserting alignment pin 23 through hole 50 of flexible circuit carrier40 and through hole 54 of substrate 52. Because apertures 44 of flexiblecircuit carrier 40 are staggered in the same format as contact pads 54,each aperture 44 should be properly aligned above a respective contactpad 54 and preferably superimposed over each aperture 44. Once flexiblecircuit carrier 40 is properly aligned above substrate 52, portions ofleads 49 which are bridged over apertures 44 are also bridged overassociated contact pads 54. Gap 57 (FIG. 7), however, separates leads 49from contact pads 54.

In order to achieve contact of the portion of each of leads 49 whichbridge or suspend respective apertures 44 with associated contact pads54, castellated nozzle 10 of the present invention may be employed andcan be aligned on top of flexible circuit carrier 40. The staggeredformat of castellations 12 permits proper alignment and superimpositionof each castellation 12 with each aperture 44 and underlying contact pad54. In order to facilitate alignment of castellated nozzle 10 toflexible circuit carrier 40 and substrate 52, alignment pin 23 may beinserted into alignment means 22 of castellated nozzle 10. Springs 34protruding from the second row 16 of castellations 12 and channels 18may be employed to balance castellated nozzle 10 on top of flexiblecircuit carrier 40, thereby preventing nozzle 10 from tipping over. Oncealignment has been achieved, castellated nozzle 10 may be forced in adirection so that each individual lead 49 is displaced into contact witha respective contact pad 54. Typically, 100 grams of force may beapplied to effect contact. In order to melt each solder coating 58,nozzle head 78 of HAT tool 70 may be brought into close proximity to thebottom of castellated nozzle 10 so that a gas may be injected into thebottom of opening 20 of castellated nozzle 10. HAT tool 70 and opening20 insures a uniform laminar flow of gas through opening 20 and intoeach channel 18. Even though each lead 49 is in contact with arespective contact pad 54, the channels 18 facilitate the escape of gastherethrough. Each channel 18 therefore acts like a chimney. Channels 18provide uniform temperature distribution of the gas at each solderlocation.

The high velocity gas can melt the solder coating 58 so as to facilitatesolder bonding of each lead 49 of flexible circuit carrier 40 torespective contact pads 54 of substrate 52. The gas passes throughopening 20 and through channels 18 of castellated nozzle 10. As the gaspasses through the channels, the solder coating 58 melts, and eddies inthe solder coating 58 are created, further facilitating solder bondingof the leads 49 to the contact pads 54. Once the solder coating 58 ismelted and the surface oxide dispersed, the molten solder wets thesolder wettable surface on leads 49. The leads 49 are then cooled toform the joint structure as shown in FIG. 9.

FIG. 9 depicts, in cross-section, and blown-up, a partial view of theresultant joint which may be achieved by the apparatus and method asdescribed herein. As can be seen in FIG. 9, the leads 49 have beenvertically displaced by the castellations 12 of castellated nozzle 10.

FIG. 10 shows a semiconductor chip packaging structure, such as amulti-chip module 80, interconnected to a semiconductor packagingsubstrate, such as printed circuit board 52. Four flexible circuitcarriers 40 of the present invention have been employed to achieveconnection of the two semiconductor devices.

FIG. 11 depicts from the side, the multichip module 80 connected to theprinted circuit board 52 through the flexible circuit carrier 40 of thepresent invention, showing the Z-shape configuration of flexible circuitcarrier 42.

While several aspects of the present invention have been described anddepicted herein, alternative aspects may be effected by those skilled inthe art to accomplish the same objectives. For example, the exactconfiguration of the castellations of the castellated nozzle of thepresent invention may be modified depending upon the configuration andsize of contact pads and the apertures of the two semiconductor devicesdesired to be connected. Accordingly, it is intended by the appendedclaims to cover all such alternative aspects as fall within the truespirit and scope of the invention.

What is claimed:
 1. A castellated nozzle for connecting a plurality ofleads to a plurality of contact pads, comprising:a body having aplurality of castellations protruding therefrom, each of saidcastellations having a contact surface thereon; a plurality of channels,each of said plurality of channels being formed adjacent to at least onecastellation of said plurality of castellations; an opening extendingthrough said body for introducing a gas therein; and means for aligningsaid contact surfaces of said plurality of castellations to a respectiveplurality of leads.
 2. The castellated nozzle of claim 1 furthercomprising a first row of castellations and channels and a second row ofcastellations and channels, said opening separating said first row fromsaid second row.
 3. The castellated nozzle of claim 2, wherein saidopening defines a first inner wall opposing a second inner wall, whereinsaid first and second inner walls are substantially parallel to oneanother.
 4. The castellated nozzle of claim 2, wherein said opening hasa bottom open end and a top open end, said top open end being proximateto said contact surfaces of said plurality of castellations.
 5. Thecastellated nozzle of claim 3, wherein said first inner wall forms aninner edge of said first row of castellations and channels and saidsecond inner wall forms an inner edge of said second row ofcastellations and channels.
 6. The castellated nozzle of claim 5,wherein said first inner wall is formed at substantially a ninety-degreeangle to said contact surfaces of said first row of castellations andsaid second inner wall is formed at substantially a ninety-degree angleto said contact surfaces of said second row of castellations.
 7. Thecastellated nozzle of claim 5, wherein each of said contact surfaces hasan outer edge formed thereon.
 8. The castellated nozzle of claim 7,wherein each of said plurality of castellations forms a planar surfaceextending from the outer edge of said contact surface to an outer wallof said castellated nozzle body.
 9. The castellated nozzle of claim 8,wherein said contact surface intersects said planar surface at saidouter edge of each of said plurality of castellations.
 10. Thecastellated nozzle of claim 5, wherein each of said plurality ofchannels in said first row forms a first channel surface extending fromsaid inner edge of said first inner wall to said outer wall of saidcastellated nozzle body, and each of said plurality of channels in saidsecond row forms a second channel surface extending from said inner edgeof said second inner wall to said outer wall of said castellated nozzlebody.
 11. The castellated nozzle of claim 1, wherein said means foraligning comprises a hole formed through said castellated nozzle body.12. The castellated nozzle of claim 11, wherein said hole has alongitudinal axis that passes through said castellated nozzle body in adirection substantially parallel to said inner wall of said opening. 13.The castellated nozzle of claim 12, further comprising an alignment pinfor insertion into said hole.
 14. The castellated nozzle of claim 13,further comprising means for balancing said castellated nozzle so thateach of said contact surfaces rests evenly on a respective lead.
 15. Thecastellated nozzle of claim 14, wherein said means for balancing saidcastellated nozzle comprises a spring attached to said castellatednozzle body, said spring having a longitudinal axis disposed parallel tosaid inner wall.
 16. The castellated nozzle of claim 15, wherein saidspring is inserted into a bore passing through said planar surface andsaid channel surface.
 17. A castellated nozzle for connecting aplurality of leads to a plurality of contact pads, comprising:a firstplurality of castellations forming a first row thereof, each of saidfirst plurality of castellations having a contact surface thereon; afirst plurality of channels formed adjacent to at least one castellationof said first row; a second plurality of castellations forming a secondrow thereof, each of said second plurality of castellations having acontact surface thereon; a second plurality of channels formed adjacentto at least one castellation of said second row; an opening formedbetween said first row and said second row, said opening having alength; said first and second plurality of castellations being arrangedin a staggered format wherein at a first point along the length of theopening one of said castellations in said first row is located oppositeto one of said channels in said second row, and wherein at a secondpoint along the length of the opening one of said channels in said firstrow is located opposite to one of said castellations in said second row;and means for aligning said plurality of castellations to a respectiveplurality of leads.
 18. The castellated nozzle of claim 17, wherein saidmeans for aligning said castellated nozzle comprises a hole positionedbetween said first and second rows for receiving a pin to secure andalign said flexible circuit carrier to said nozzle.
 19. The castellatednozzle of claim 18, further comprising a pin for insertion into saidhole.
 20. The castellated nozzle of claim 17, wherein said opening iselongate and separates said first and second rows of castellations, saidopening having a bottom open end and a top open end.
 21. The castellatednozzle of claim 20, further comprising a hot air thermode tool forintroducing a gas into the bottom open end of said opening.